Certain engine blocks, such as V-blocks or Y-blocks, include a number of cylindrical bores on each side of the block which extend into a block at a common angle inclined from the vertical axis. For a given block, the central axes of the bores of one side will intersect with the central axes of the bores of the other side to form an angle, referred to herein as the "V angle." The V angle will represents twice the value of the inclination of each bank of cylinders from the vertical axis.
One common type of machine for reboring the cylinders of an engine block employs a boring tool which is rotatably mounted on a vertically disposed shaft. The boring tool is lowered along a vertical pathway into a cylinder to rebore the cylinder. It is thus necessary for proper reboring that the cylinder be aligned under the boring tool and oriented such that its central axis is vertical.
Boring machines designed for use with engine blocks having a plurality of cylinders aligned in a row, referred to hereinafter as a "bank" of cylinders, are commonly mounted on a planar slide surface. Such an arrangement enables the machine to be slid over each successive cylinder in a bank, thereby allowing all the cylinders in a given bank to be rebored while the block is fixtured in a single position. Sliding of the machine along the planar slide surface is normally restricted to a straight-line pathway so that if the first cylinder in a bank is properly aligned with the machine and fixtured in place, the remaining cylinders will also be properly aligned.
In order to properly align a V-block or Y-block so that an entire bank of cylinders can be rebored from a single fixtured position, it is necessary to incline the block so that the cylindrical bores are in a vertical position. The block must then be vertically and horizontally aligned or "indexed" with respect to the planar slide surface so that the boring tool can be lowered into each cylinder with its central axis positioned substantially in the same position as the central axis of the cylinder.
One known method of aligning and fixturing a V-block or Y-block is to mount the block on a mounting fixture known as a "sled." A conventional sled comprises a triangular solid having cross-sections forming right triangles and a planar mounting surface formed by the hypotenuse of the triangular cross-sections. The mounting surface is inclined from the horizontal at an angle which is equal to half the V-angle of the block, so that when the bottom of a block is mounted on the sled and properly aligned on the mounting surface, one bank of cylinders will be in a vertical position, as required for reboring. (When referring to the "bottom" of an engine block herein, it is of course understood that the pan rail which forms the bottom of the block is often irregularly shaped. The main bearing caps, for example, will project downwardly from the block when in place. The lower portion of a block will, however, generally form a plane which is referred to herein as the bottom of the block.)
An example of a conventional sled is illustrated in FIG. 8. The sled includes a securing bar which is adjustably positioned parallel to and spaced apart from the planar mounting surface to harness a block between the planar mounting surface and the securing bar. Bracket assemblies positioned on each end of the planar mounting surface support a pair of threaded column members which extend outwardly from the planar mounting surface through the securing bar. Wing nuts fit on the projecting ends of the column members to allow the securing bar to be tightened down to secure a block to the sled. Proper alignment of the block on the sled is ensuring by an alignment bar which is inserted through the main bearing housing of the block and fixtured within openings in the bracket assemblies to align the block with respect to the sled.
In a conventional arrangement, an engine block is placed on the mounting surface, properly aligned using the alignment bar, and secured in place by tightening the securing bar down. The sled and engine block may then be moved as a unit using a hoist or the like and placed on the base assembly of a boring machine beneath the boring tool. The base assemblies normally include a pair of slide surfaces on which the sled may be placed for proper adjustment and alignment with respect to the boring machine. Some machines utilize base assemblies having a spindle on which a sled may be placed for easy rotation and adjustment.
Conventional sleds enable engine blocks to be mounted on a sled with or without the main bearing caps of the block in place. When the main bearing cap of a V-block is in place, it is necessary to use an elevating frame on the mounting surface to support the bottom portions of the block on either side of the main bearing cap. The frame is necessary because the main bearing cap projects outwardly beyond the bottom of the block. Without some means of supporting the outer portions of the bottom of an engine block, the block would tilt out of alignment with the mounting surface and the cylinders would no longer be in a vertical position.
Although existing sleds provide a means for fixturing V- and Y-blocks, several disadvantages remain with existing models. One disadvantage is that a separate sled is required for blocks having different V-angles. For example, a sled designed for a 60.degree. V-angle block cannot be used with a 90.degree. V-angle block. Another disadvantage is that the fixturing process is relatively slow. In many arrangments, it is necessary to fixture a block twice on the sled in order to rebore both banks of cylinders. Thus, the time required for fixturing a block on the sled becomes a very important factor in the overall efficiency of the sled. It is desirable to provide an arrangement which facilitates relatively quick fixturing to minimize the time expended here. Another disadvantage of existing sleds is that they can often be bulky and difficult to handle. It is desirable to provide a sled which will be easy to maneuver by the operator and include safety features to reduce the chance of accidentally dropping the sled on the operator.